A few things I would have done differently …

I was at Montclair Park in Oakland the other day, spending some time with my 4-year-old. For the first time at the playground, I got that “high-school-grad-who-keeps-going-to-the-homecoming-game” feeling. Most of the kids were younger, and the other fathers were in that super-energetic/overcompensating mode. (Not judging. I was doing the exact same thing with my older son 5 years ago.)

The feeling of disconnection was strong. I was no longer in need of potty training tips or ideas for cool outings to kill time for a pre-schooler. The old small talk didn’t apply any more.

Me: “How many months old is she?”

Mother pushing kids on swing: “Ten months. And yours?”

Me: “He’s 53 months. And I have a 88-monther at home …”

With my youngest son enjoying his last preschool year, going to the playground or Children’s Fairyland or planning a stuffed animal birthday party is less of a routine and feels more like “Last Holiday” (the Alec Guinness version, not the Queen Latifah one). You start to notice the sunsets when you only have a few left.

It doesn’t feel especially depressing. I realize that every age is going to be special in its own way. The 700 people who told me how fast it all goes by made an impact, and I tried to savor every moment.

I don’t have many regrets. But I thought I’d pass on a few. Yours in the comments …

If I could do it again, I would …

* Teach my sons more of the fundamentals: I was awesome at building couch cushion forts, going on kite-flying excursions, discovering new parks and organizing Giraffey’s 47 birthday parties. But I was terrible about things like bike-riding, baseball catching, swimming lessons and shoe-tying skills. I wish I had a checklist and focused on more of the basics.

* Build a treehouse … or a playhouse or some other space on our property that was child dedicated. My parents remodeled our house when I was 4 years old, and my dad and our carpenter crafted a little kid-friendly loft (maybe 30 square feet total) in the attic above my room. It was like my little Camp David. I had sleepovers and read books there when I was little, and had a place to hide my weed when I was in high school. Wait …

* Yell less: Not a lot less. My kids needed to know who was in charge. But I could have probably eliminated 30 percent of the yelling with more creative forms of communication. Sometimes the yelling was just out of laziness, because finding a positive way to convey urgency takes longer/more energy.

* Enter the Super-Crafty Halloween Costume Contest … which is coming back to The Poop for the 6th time next month! Look for an announcement around Oct. 7 or 8. In general, I should have done more crafty things with my kids. But this was an obvious one. I always feel a lot bit guilty buying my kid a store-made Clonetrooper costume when all of you are slaving over a hot glue gun.

* Buy the Merritt Bakery hamburger cake: It seemed indulgent, and the cake looks like it’s about 75 percent frosting. But I’ve found that when you buy something special, the memory is often worth more than the expense. There’s still time for this one …

* Get off of social media: Partly because of my job, I’ve taken a lot of breaks during kid/dad outings to comment on Twitter, write down stray thoughts and take photos for future posts and articles. Some of this was good for our relationship — I was able to spend more time with my children by making them a part of my work. But it often was taken too far. The breaking point was a trip to Disneyland last year, where I spent way to much time on Twitter documenting our travels. I wish I had dropped all connection to work and focused 100 percent on my family. That special memory is slightly tainted because I wasn’t completely there.

My 4-year-old just asked me to set up the Hot Wheels tracks with him. (Only the old school tracks — not of that T-Rex Splash Zone crap.) This is a reminder that I should be looking forward, not back.

But I still want to hear from you. If you could get the younger parenting years back, what would you do differently?

PETER HARTLAUB is the pop culture critic at the San Francisco Chronicle and founder of this parenting blog. Follow him on Twitter @PeterHartlaub. Friend the The Poop on Facebook.